1. Field of the Invention
The present invention relates to a metallic mold for molding semiconductor package and, more particularly, pertains to a metallic mold for molding semiconductor package which includes an upper cavity block having two types of series of cavities at, respectively, upper and lower surfaces thereof, and a lower cavity block also possessing such two types of series of cavities at, respectively, the upper and lower surfaces thereof. Each of the upper cavities of the upper cavity block is adapted to mate with each of the lower cavities of the lower cavity block, and each of the lower cavities of the upper cavity block is adapted to mate with each of the upper cavities of the lower cavity block, so as to enable two types of molded products to be manufactured by employing only the pair of cavity blocks, thereby increasing the degree of productivity in the manufacture of semiconductor packages.
2. Description of the Prior Art
In general, a process for manufacturing semiconductor packages, subsequent to semiconductor chip having been attached to the inner leads of a lead frame such that bonding pads of the semiconductor chip are electrically connected to the respective inner leads of the lead frame, provides for the step that the semiconductor chip and the inner leads which have been connected to each other are encapsulated by a molding compound in order to form a specifically configured semiconductor package.
Referring to FIG. 1, there is shown a conventional molding die which is used to mold semiconductor packages as described herein above. As shown in the drawing, the molding die is generally divided into an upper mold die "T" and a lower mold die "B".
The upper mold die "T" includes a top mold base 10 and a top chase block 11 which is mounted on a lower surface of the top mold base 10 by means of screws. A top ejector plate 17 and a top drive plate 18 are mounted on the top mold base 10. A top return pin 19 is fixed to the top ejector plate 17 and protrudes downwardly. A support pin 19a is fixed to the top drive plate 18 in order to support the top return pin 19. Moreover, the top return pin 19 is inserted through holes in the top mold base 10 and the top chase block 11 so as to enable the top ejector plate 17 and the top drive plate 18 to be moved either upwardly and downwardly.
The top chase block 11 has a top center block 12 located in the center of its interior. The top center block 12 is closely fixed to a lower surface of the top mold base 10 by means a suitable locking block (not shown). The top center block 12, which is fixed in the top chase block 11, is formed at its lower surface with runners 12a and gates 12b adapted to be in communication with the runners 12a such that a resin in a gel state can be introduced into the runners 12a and the gates 12b through a pot (not shown).
Upper cavity blocks 13, at a lower surface of which there are formed a plurality of upper cavities 13a, are mounted at both sides of the center block 12 in the chase block 11. An upper pillar supporting plate 15 having a plurality of holes is mounted on each of the upper cavity blocks 13. A plurality of upper pillars 14, each of which corresponds to and is inserted into each of the holes of the upper pillar supporting plate 15, are interposed between the upper pillar supporting plate 15 and the top mold base 10, so that the plurality of pillars 14 support the upper cavity blocks 13 through the pressure of the top mold base 10. A locking block 16 is interposed between the outer side of each of the cavity blocks 13 and inner surface of the top mold base 10.
On the other hand, the lower mold die "B" includes a bottom mold base 20 and a bottom chase block 21 which is mounted on an upper surface of the bottom mold base 20 by means of fastening screws. A bottom ejector plate 27 and a bottom drive plate 28 are mounted on the bottom mold base 20. A bottom return pin 29 is fixed to the bottom ejector plate 27, and protrudes upwardly. A support pin 29a is fixed to the bottom drive plate 28 for the purpose of supporting the bottom return pin 29. Additionally, the bottom return pin 29 is inserted through holes in the bottom mold base 20 and the bottom chase block 21 so that the bottom ejector plate 27 and the bottom drive plate 28 can be moved either upwardly or downwardly. A clamping block 29b is located under the bottom drive plate 28.
The bottom chase block 21 has a bottom center block 22 located in center of its interior. The bottom center block 22 is closely fixed to an upper surface of the bottom mold base 20 by means of a locking block (not shown).
The bottom center block 22 which is fixed in the bottom chase block 21 is formed with runners 22a at both sides of upper surface thereof which are in communication with the runners 12a of the top center block 12.
Lower cavity blocks 23, at an upper surface of which there is formed a plurality of lower cavities 23a and gates 23b which are each in communication with each of the lower cavities 23a, are mounted at both sides of the bottom center block 22. Between the outer side of each of the cavity blocks 23 and the inner surface of the bottom mold base 20 there is interposed a locking block 26 in order to provide a fastening for the lower cavity block 23.
A lower pillar supporting plate 25 having a plurality of holes is mounted on a lower surface of each of the upper cavity blocks 23. A plurality of lower pillars 24, each of which corresponds to and is inserted in each of the holes of the lower pillar supporting plate 25, are interposed between the lower pillar supporting plate 25 and the bottom mold base 20 such that the plurality of pillars 24 support the lower cavity block 23 through pressure of the bottom mold base 20.
Accordingly, the conventional metallic mold for molding semiconductor package comprises the upper cavity block 13 having a plurality of upper cavities 13a at its lower surface and the lower cavity block 23 having a plurality of lower cavities 23a at its upper surface, in a manner whereby each of the upper cavities 13a of the upper cavity block 13 mates with each of the lower cavities 23a of the lower cavity block 23 to form a pair of molds for molding the shapes of semiconductor packages.
In this description of the conventional mold, although a plurality of other components besides the components shown in the drawing are associated with the upper mold die "T" and the lower mold die "B" so as to inject molding resin in a gel state into the cavities 23a and 13a through the runners 12a of the top center block 12, those other components are not illustrated in the drawing because the invention only concerns itself with the cavity blocks.
The operation of the mold die for semiconductor packages possessing the above-mentioned prior art mold for molding semiconductor packages is now described as follows:
First, after semiconductor chips which are wire-bonded to respective lead frames, are placed on the lower cavity blocks 23, the upper molding die "T" and the lower molding die "B" are clamped to each other such that each of the upper cavities 13a of the upper cavity blocks 13 faces each of the lower cavities 23a of the lower cavity block 23 which corresponds to the upper cavity 13a. Thereafter, as a plunger (not shown) is inserted downwardly into the upper molding die "T", molding resin is supplied to the pot of the upper molding die "T" and injected into the runners 12a and the gates 12b of the top center blocks 12. Thereafter, the molding resin is injected into the upper and lower cavities 13a and 23a through the gates 22a of the bottom center block 22 and the gates 23b of the lower cavity blocks 23.
Consequently, since the series of upper cavities 13a of the upper cavity block 13 and the series of lower cavities 23a of the lower cavity block 23 constitute only one type of molding shape, the conventional cavity blocks can mold only one type of molded products.
On the other hand, in order to manufacture another type of semiconductor packages, after the locking blocks are separated from the fastened together upper and lower cavity blocks 13 and 23, the upper and lower cavity blocks 13 and 23 are simultaneously pulled out of the upper and lower chase blocks 11 and 21. Thereafter, separate upper and lower blocks which are formed with another shape of cavities are inserted into the upper and lower chase blocks 11 and 21. The mold die is then operated in the above-mentioned manner so as to mold another shape of semiconductor packages.
As described above, the cavity blocks have been known as the most important components in a molding die for molding semiconductor package. In addition, since each of the cavity blocks must be formed with several tens or hundreds of cavities and runners for guiding resin to the cavities by super-precise electro-discharge machining, the cavity blocks are the most expensive components.
However, since the above-mentioned conventional metallic mold for molding semiconductor packages possesses one type of cavities capable of molding only one shape of semiconductor packages, it is necessary to prepare separate and expensive cavity blocks having another shape of cavities when it is intended to manufacture another shape of semiconductor packages, thereby increasing the costs of manufacture. Furthermore, since there is required a lengthy period of time for installing separate upper and lower cavity blocks in a molding die, the productivity is lowered for molding the products.